Liquid cooled rotor housing

ABSTRACT

A liquid cooled rotor housing for a rotary piston internal combustion engine in which the rotor housing includes an outer annular shell and an inner annular shell with circumferentially spaced interconnecting ribs therebetween forming with the walls of the shells&#39;&#39; fluid passages for cooling liquid, the shells being further interconnected with circumferentially extending and axially spaced apart hoop struts to reduce the housing&#39;&#39;s vibratory amplitude while raising the inner shell&#39;&#39;s natural frequency to thereby reduce trochoid surface chatter.

United States Patent [191 Flynn, Jr. et al.

[ 51 Jan. 21,1975

[ LIQUID COOLED ROTOR HOUSING [75] Inventors: Gregory Flynn, Jr., St. Clair Shores;

Paul J. Louzecky, Troy, both of Mich.

[73] Assignee: General Motors Corporation,

Detroit, Mich.

[22] Filed: Oct. 10, 1973 21 App]. No.: 404,859

[52] U.S. Cl. 418/83, 123/801 [51] Int. Cl.... F01c 21/06, F04c 29/04, F02b 55/10 [58] Field of Search 418/83; 123/801 [56] References Cited UNITED STATES PATENTS 5/1965 Bentele et a1 418/83 4/1967 Ito et a1. 418/83 6/1971 Toyama et al. 418/83 FOREIGN PATENTS OR APPLICATIONS 974,370 11/1964 Great Britain 418/83 Primary ExaminerJohn .1. Vrablik Attorney, Agent, or Firm-Arthur N. Krein [57] ABSTRACT A liquid cooled rotor housing for a rotary piston internal combustion engine in which the rotor housing includes an outer annular shell and an inner annular shell with circumferentially spaced interconnecting ribs therebetween forming with the walls of the shells fluid passages for cooling liquid, the shells being further interconnected with circumferentially extending and axially spaced apart hoop struts to reduce the housings vibratory amplitude while raising the inner shells natural frequency to thereby reduce trochoid surface chatter.

5 Claims, 3 Drawing Figures LIQUID COOLED ROTOR HOUSING This invention relates to rotary piston internal combustion engines and, in particular, to the liquid cooled rotary housing for such an engine or similar rotary mechanism.

A rotary piston internal combustion engine includes a housing having a hollow rotor housing partly enclosed by end housing cover plates to provide a cavity therein in which a rotor is suitably supported for planetary rotation. The inner surface of the rotor housing has a multilobe profile, of epitrochoidal figuration, or based on such a general configuration. The rotor has end faces disposed adjacent to the inner walls of the end housing cover plates for sealing cooperation therewith and has a peripheral surface with a plurality of circumferentially spaced apex portions, each of which carries an axially extending movable apex seal for sealing engagement with the multilobed inner surface of the rotor housing, the rotor with the apex seals thus forming with the inner walls of the housing a plurality of variable volume working chambers upon relative rotation of the rotor in the housing.

In order to effect cooling of such a rotary piston engine, it has been customary to provide coolant fluid passages in the rotor housing, these being formed by providing the rotor housing with a continuous annular inner wall or shell from which a plurality of spacedapart cross ribs or struts project radially outward and interconnect with an outer wall or shell of the rotor housing. These ribs or struts normally extend axially across the rotor housing but may be inclined relative to the axis of the rotor housing.

In the operation of such a rotary piston engine, it has now been found that one source of apex seal chatter is excitation from the vibration of the rotor housing. Thus, as an apex seal contacts or rides on the inner surface of the rotor housing and, depending upon the natural frequency of vibration, the seal chatter is either amplified or dampened depending on the system characteristics. In the conventional rotor housing structure as described above, the present cross strut or rib arrangement results in many unsupported inner wall or shell sections of the rotor housing which can vibrate. In addition, the inner and outer walls or shells can also vibrate with nodule points at the cross struts or ribs.

It is therefore the principal object of this invention to improve a liquid cooled rotor housing structure for use in a rotary piston internal combustion engine whereby the inner and outer shells of a rotor housing are circumferentially interconnected to thereby reduce apex seal chatter during engine operation.

Another object of this invention is to improve a rotor housing structure adapted to be liquid cooled whereby the apex seal chatter can be reduced by reducing the rotor housing vibratory amplitude while the air portion of the housing natural vibration frequency is erased.

These and other objects of the invention are attained by means of a liquid cooled rotor housing for a rotary piston internal combustion engine in which the housing is formed as an integral structure with spaced apart inner and outer shells interconnected by circumferentially spaced-apart cross ribs or struts to form therewith coolant fluid passages, the shells being further interconnected by sets of spaced-apart circumferential stiffeners or hoop struts, the sets of stiffeners or hoop struts overlapping circumferentially whereby the inner and outer shells are circumferentially interconnected.

For a better understanding of the invention as well as other objects and further features thereof, reference is had to the following detailed description of the invention to be read in connection with the accompanying drawings wherein:

FIG. 1 is a transverse sectional view through a rotary piston internal combustion engine having a liquid cooled rotor housing in accordance with the invention:

FIG. 2 is a sectional view along the shaft axis of the engine of FIG. 1; and

FIG. 3 is an enlarged sectional view taken along Line 33 of FIG. 1.

Referring now to FIGS. I and 2, there is illustrated a rotary piston internal combustion engine, generally indicated by reference numeral 10, having a liquid cooled engine housing including a hollow rotor housing 12 partly enclosed at opposite ends by end housing cover plates 14 and 16, suitably secured together as by bolts 17, to form a cavity 18. A rotor 20 is rotatively mounted in the cavity 18 on an eccentric shaft 22 suitably journaled in the housing with the axis of the eccentric shaft extending longitudinally through the hollow rotor housing.

Planetary movement of the rotor 20 is effected by the eccentric portion 22a of the shaft 22 and by means of an internal gear 24 fixed to the rotor 20 and a gear 26 fixed coaxial to the axis of rotation of the eccentric shaft 22.

The engine is also provided with an inlet manifold 34 and an outlet manifold 36 connected to inlet port 38 and outlet port 40, respectively, in the housing. Suitable means, such as a spark plug, not shown, may be provided to initiate combustion of an air-fuel mixture delivered to the working chambers of the engine or the engine may be operated as a diesel engine with fuel injection.

During engine operation, heat generated within the engine is dissipated by flowing coolant fluid through the engine housing, including the rotor housing portion thereof. Preferably, the coolant fluid flows in at least two flow paths through the rotor housing; that is, the fluid would first flow in one direction through a portion of the rotor housing and then in the opposite direction through another portion of the rotor housing. The use of three or more coolant flow paths in this type engine is also practical to effect a more uniform temperature gradient around various sections of the engine.

For this purpose, the rotor housing is provided with passages, between the inner peripheral wall and outer peripheral wall of this housing, for the flow of coolant fluid therethrough from one cover plate 14 of I6 to the other with suitable coolant inlet and discharge ports, not shown, being provided, for example, in cover plate 14.

Thus, during engine operation, heat generated within the engine housing is dissipated by flowing coolant fluid from and to suitable chamber 42 and at least one chamber 42a in the cover plate 14 and interconnecting chamber 44 and at least one chamber 44a in the cover plate 16, these chambers in the cover plates being serially interconnected by axially extending coolant fluid passages 46 in the rotor housing. In addition, chamber 42 and one of the chambers 42a are connected, respectively, to an inlet port and an outlet port, not shown, for the ingress and egress of coolant fluid to the engine,

while the chambers 44 and 44a in cover plate 16 are connected in a suitable manner, not shown, so that coolant fluid entering the engine housing will flow from the chamber 42 in cover plate 14 through one or more fluid passages 46 in the rotor housing to a chamber in the cover plate 16, the coolant fluid then returning from cover plate 16 through another one or more passages 46 to a chamber 42a in cover plate 14 for final discharge therefrom. It is to be realized if more than two groups of passages 46 are provided through the rotor housing, the coolant fluid can be further cycled, as previously described, through the engine housing, as desired.

Referring now to the rotor housing 12 of the invention, the rotor housing, as best seen in FIG. 1, is formed with an inner annular wall or shell 60, the inner surface of which has a multilobe profile forming the surface 32, and an outer wall or shell 62, the inner and outer shells being interconnected together by circumferentially spaced apart parallel cross ribs 64 and the circumferentially extending, axial spaced-apart stiffeners or hoop struts 66 formed integral with the inner and outer shells and with the cross ribs 64 or with the apertured fastener receiving bosses 68 which extend the full axial length of the rotor housing. Preferably, both the ribs 64 as well as the bosses 68 are apertured to receive the bolts 17. Selected cross ribs 64 may also be apertured, as desired, to provide oil or other fluid passages 70, as desired, through the rotor housing between the end covers 14 and 16.

In the embodiment shown, both the ribs 64 and the bosses extend in a direction parallel to the rotative axis of shaft 22, but it is to be realized that the ribs may be inclined, as desired, either relative to the axis of the shaft 22 or radially. Also, both the cross ribs 64 and the bosses 68 may be of any desired circumferential width or shape and have any desired circumferential spacing between the inner shell 60 and outer shell 62, it being realized that the spacing between cross ribs 64 define the circumferential width of a passage 46 since the opposing walls of a set of cross ribs form the side walls of a passage 46 while the other set of walls of the passage are defined ,by the inner surface of outer shell 62, including the bosses 68 thereon and by the outer surface of inner shell 60.

The bosses 68 are formed integral with the outer shell 62 and extend radially inward therefrom with the outer peripheral surface of each boss spaced from the outer peripheral wall of inner shell 60 whereby a greater surface area of the inner shell will be in thermal heat exchange relationship to the coolant fluid flowing through the rotor housing between the inner and outer shells thereof. However, even though the outer shell is not connected to the inner shell by these struts, the sections of these shells adjacent to the bosses are interconnected by means of the circumferential hoop strut 66 formed integral with its boss in adjacent portions of the inner and the outer shells. As best seen in FIG. 3, the opposing sets of hoop struts, whether extending from a cross rib 64 or a boss 68, are spaced axially apart from each other but each such set of hooped struts 66 overlap each other in a circumferential direction between the inner shell 60 and outer shell 62 whereby no peripheral section of these shells is not supported circumferentially by either a cross rib 64 or a hoop strut 66.

Preferably, the hoop struts are arranged at a suitable angle relative to the desired coolant flow path and preferably the opposing hoop struts of a set of hoop struts; that is, alternate struts, are of different thickness, as seen in FIG. 3, in order to change the frequency of housing vibration in a different section of the rotor housing.

The struts 66 extending from the inner shell 60 to the outer shell 62 tie both shells together and provide greater support to the entire rotor housing than the conventional design. The inner housing therefore, in order to vibrate, must now engage the outer housing. This increase in housing stiffness raises the natural frequency of the epitrochoidal surface 32 upon which the apex seal 71 travels. This improved inner surface support also reduces the ability of the inner surface to vibrate. The struts 66 also connect the inner housing 60 and outer housing 62 circumferentially which prevent the formation of nodal points or points of inflection along the inner housing surface within the engine operating speed range.

The housing vibration excites the apex seal which then starts pounding on the housing surface causing housing surface chatter or waves on the inner housing surface. These chatter marks are somewhat similar to the washboard pattern found on many dirt country roads and it is the formation of these chatter marks that the struts are trying to prevent.

The housing, besides vibrating in a circumferential whipping pattern as just described, often tends to vibrate across the rotor housing surface. By placing the cross struts 66 at an angle across the housing surface, FIG. 3, the struts provide additional support to the rotor surface. FIG. 3 only shows one set of struts 66 on supports 64 and 68. However, if need be, more than one set of struts could be used to support these surfaces. These additional struts providing additional support would further raise the natural frequency of the housing.

Reducing the housing vibration also reduces the engine friction losses as the apex seals 71 can now slide on the housing surface and not follow some undulating pattern.

Also, it is to be realized that the struts 66 need not be placed symmetrically on the supports, as shown in FIG. 3, but could be staggered, as desired. The struts 66 besides reducing the tendency of the housing to vibrate also provide greater housing support for better thermal stress distribution.

What is claimed is:

l. A rotor housing for a rotary piston internal combustion engine, said rotor housing including an annular inner shell having an inner surface with a multilobe profile, an outer shell encircling said inner shell and spaced from said inner shell, a plurality of circumferentially spaced-apart cross ribs extending across the full width of said inner shell and said outer shell connecting said inner shell to said outer shell and forming therewith fluid coolant passages for the flow of fluid across the full width of said rotor housing, and circumferential extending, axial spaced-apart hoop struts extending from opposite sides of said cross ribs to further connect said inner shell to said outer shell, an adjacent set of said hoop struts peripherally overlapping each other around the outer periphery of said inner shell intermediate the ends thereof.

2. A rotor housing according to claim 1, wherein one of said hoop struts of an adjacent set of said hoop struts is of a greater thickness than the other of said hoop struts in said set.

3. A rotor housing according to claim 1 further including circumferentially spaced-apart apertured boltreceiving bosses extending radially inward from said outer shell between said spaced-apart cross ribs, the outer surfaces of said bosses being spaced from the outer peripheral surface of said inner shell, and circumferential extending, axial spaced-apart hoop struts integral with each of said bosses on opposite sides thereof.

4. A rotor housing for use in a rotary mechanism having a housing including said rotor housing, which is hollow with an inner peripheral surface having a multilobe profile, partly enclosed at opposite ends by end housing cover plates to define a rotor cavity, a rotor rotatively mounted in the rotor cavity on an eccentric shaft journaled in the end housing cover plates with the axis of the shaft extending longitudinally through the rotor housing, said rotor housing including an annular inner shell, the inner surface of which has the multilobe profile, an annular outer shell spaced from and encircling said inner shell, a plurality of circumferentially spacedapart ribs interconnecting said inner shell to said outer shell and forming therewith fluid passages. a plurality of circumferentially spaced-apart apertured boltreceiving bosses extending rdaially inward from said outer shell between said cross ribs, said bosses terminating in spaced radial relation from said inner shell and, circumferentially, extending, axial spaced-apart hoop struts integral with said cross ribs and said bosses further interconnecting said inner shell to said outer shell with adjacent hoop struts overlapping each other in a peripheral direction around said inner shell.

5. A rotor housing according to claim 4 wherein alternate hoop struts of said hoop struts are of a greater thickness than the remainder of said hoop struts. 

1. A rotor housing for a rotary piston internal combustion engine, said rotor housing including an annular inner shell having an inner surface with a multilobe profile, an outer shell encircling said inner shell and spaced from said inner shell, a plurality of circumferentially spaced-apart cross ribs extending across the full width of said inner shell and said outer shell connecting said inner shell to said outer shell and forming therewith fluid coolant passages for the flow of fluid across the full width of said rotor housing, and circumferential extending, axial spaced-apart hoop struts extending from opposite sides of said cross ribs to further connect said inner shell to said outer shell, an adjacent set of said hoop struts peripherally overlapping each other around the outer periphery of said inner shell intermediate the ends thereof.
 2. A rotor housing according to claim 1, wherein one of said hoop struts of an adjacent set of said hoop struts is of a greater thickness than the other of said hoop struts in said set.
 3. A rotor housing according to claim 1 further including circumferentially spaced-apart apertured bolt-receiving bosses extending radially inward from said outer shell between said spaced-apart cross ribs, the outer surfaces of said bosses being spaced from the outer peripheral surface of said inner shell, and circumferential extending, axial spaced-apart hoop struts integral with each of said bosses on opposite sides thereof.
 4. A rotor housing for use in a rotary mechanism having a housing including said rotor housing, which is hollow with an inner peripheral surface having a multilobe profile, partly enclosed at opposite ends by end housing cover plates to define a rotor cavity, a rotor rotatively mounted in the rotor cavity on an eccentric shaft journaled in the end housing cover plates with the axis of the shaft extending longitudinally through the rotor housing, said rotor housing including an annular inner shell, the inner surface of which has the multilobe profile, an annular outer shell spaced from and encircling said inner shell, a plurality of circumferentially spaced-apart ribs interconnecTing said inner shell to said outer shell and forming therewith fluid passages, a plurality of circumferentially spaced-apart apertured bolt-receiving bosses extending rdaially inward from said outer shell between said cross ribs, said bosses terminating in spaced radial relation from said inner shell and, circumferentially, extending, axial spaced-apart hoop struts integral with said cross ribs and said bosses further interconnecting said inner shell to said outer shell with adjacent hoop struts overlapping each other in a peripheral direction around said inner shell.
 5. A rotor housing according to claim 4 wherein alternate hoop struts of said hoop struts are of a greater thickness than the remainder of said hoop struts. 